All usage event (Actual and Expected gallons) data across all zones is padded to 1-second interval data, assuming constant flowrates. Within a water source, Actual and Expected Gallons are then aggregated to the minute across all Zones. THe meter data is similarly aggregated to minute-level data. Then, minute-level usage events can be matched to minute-level meter data.
For each minute for each water source, the difference between Actual (metered) and Expected gallons is computed by simple subtraction. The Actual and Expected Gallons time series plots below are interactive via zoom and pan.